A Bankart lesion is a tear in the shoulder and typically entails the instability of the shoulder joint which occurs subsequent to a shoulder dislocation. This instability is commonly the result of a tearing of the joint capsule and its glenoid labrum, a fibrocartilaginous structure, from the anterior aspect of the glenoid. One surgical intervention for correcting the instability associated with a Bankart lesion is reattachment of the torn capsule and glenoid labrum to bone, on the anterior facet of the glenoid.
An arthroscopic Bankart repair typically involves: (i) embedding a suture anchor in a bony bed; (ii) passing a suture, which is attached to the embedded suture anchor, through the soft tissue which is to be reattached to the bony bed; and (iii) tying the soft tissue to the suture anchor, thus coapting the torn tissue to the bony bed.
Guiding small suture anchors while accurately positioning repair tissue and driving the suture anchors into bone can be excessively complex. Particularly, in an arthroscopic Bankart repair, inserting suture anchors into the glenoid rim is technically demanding, rendering the procedure extremely difficult.
In a Bankart intervention, the surgeon must visually assess the axis of the glenoid to gain access to it and see the glenoid for placement of an anchoring device, for example a bioabsorbable suture anchor. However, the deltoid muscle, tendons and other tissue obscure the glenoid neck and it is undesirable to disturb this region. Therefore, the surgeon has no visualization of the anatomy behind the face of the glenoid, particularly with regard to the thickness and orientation of the glenoid neck which does not correspond with the axis of the glenoid. Thus, there is always a risk that the anchoring device will either impinge on the sloping back wall of the neck, which will lead to unsatisfactory placement of the implant against the glenoid face, or will penetrate the cortical bone which may result in bone fracture or interference with or damage to soft tissue.
In addition, the anatomy of the glenoid itself provides very little bone into which an anchoring device can be placed. The articulating surface of the joint consists of a shallow dished cartilaginous area bonded by soft tissue of the rotator cuff which stabilizes the humeral head against the glenoid. While the lateral aspect of the glenoid presents a broad surface for articulation, its margins taper rapidly medially to form a narrow neck of about 10 to 15 mm thickness from which emerge the coracoid (superiorly) and acromial (posteriorly) processes. The thinning of the glenoid progresses into the scapula where the thickness may be as little as 2 mm to 3 mm, although there is a broader spine running along the inferior margin of the scapula. In addition, disease or degeneration can severely restrict the size of the glenoid, rendering implant placement even more problematic. For example, when an anchoring device is inserted into the articulating surface of the glenoid adjacent the damaged labrum to allow labral repair, the labrum tends to pull off the narrow and vertical articulating surface of the glenoid.
Accordingly, there is a need for an arthroscopic instrument and method that mobilizes the glenoid and the adjacent ligaments and labrum, and provides a secure platform for inserting an anchoring device, such as a suture anchor, into the glenoid to allow labral repair at a predefined specific position. There is also a need for a drill guide that is capable of limiting or controlling the depth of insertion of a drill in the bone such that a bore is formed only slightly into the glenoid face. The need also exists for a method of conducting a Bankart repair with a drill guide to a shallow predetermined depth, while minimizing the amount of bone removed and the force applied to the bone to allow the labrum to be attached as high as possible on the glenoid face relative to the glenoid articulating surface.